U.S. Pat. No. 6,103,628, assigned to the assignee of the present invention, describes a reverse linear chemical mechanical polisher, also referred to as bi-directional linear chemical mechanical polisher that operates to use a bi-directional linear motion to perform chemical mechanical polishing. In use, a rotating wafer carrier within a polishing region holds the wafer being polished. U.S. Pat. No. 6,103,628 is incorporated herein by reference.
U.S. Pat. Nos. 6,464,571 and 6,468,139, assigned to the assignee of the present invention and related to the '628 patent, describe various features of a reverse linear chemical mechanical polisher, including incrementally moving the polishing pad that is disposed between supply and receive spools. U.S. Pat. Nos. 6,464,571 and 6,468,139 are incorporated herein by reference.
While the mechanisms shown and described in these patents typically use roller bearings for supporting the polishing pad, roller bearings may have certain characteristics that affect polishing action, for example, in a reciprocating polishing apparatus, rotational momentum must be reversed whenever the belt direction is reversed. The act of overcoming roller bearing momentum may cause temporary or permanent belt stretching or other unwanted distortion, which can affect the polishing action. Additionally, while the inventions described in the patents are advantageous, further novel refinements are described herein which provide for a more efficient drive system for reverse linear, e.g. bi-directional linear, motion.